The intellectual model of Jean Piaget asserts that individuals pass through a series of various intellectual stages as they mature. Human development is categorized into four basic stages: (1) sensory motor stage, which lasts from birth to about eighteen months; (2) preoperational stage, lasting from eighteen months to about seven years; (3) concrete operational stage, which lasts from seven years to about eleven years; and (4) formal operational stage, which is attained at about eleven or twelve years and lasts throughout life. From the stage-age perspective, Piagetian theory is seriously limiting when one considers appropriate educational experiences for a group of early adolescent learners. The time an individual spends at each level varies and may be influenced by many factors, including: innate ability; biological maturation; experiences; social influences; equilibration; parent child relationship; peer influence; life role aspirations; academic overload; and cultural diversity. (CJ)